Roadway repair is often accomplished by overlaying the existing pavement (whether of concrete or asphalt paving material) with a new layer (often called a leveling course) of concrete or asphalt paving material. Without prior surface treatment, however, this method of repair generally results in the application of insufficient quantities of paving material in the rutted, potholed or otherwise damaged areas, because the overlay will be applied at the same rate per unit of roadway width in damaged areas (which have a greater depth to be filled across the width) as in the undamaged areas. The resulting reduced density in the overlay of the previously damaged areas will lead to renewed rutting or other wear damage in the new pavement in relatively short order. However, by milling the surface of the damaged pavement to a uniform surface elevation below the level of the damage, the addition of new pavement will produce a road surface having a consistent elevation across the entire width of the roadway. This repaving technique can be used to return the elevation of a damaged roadway to its original pre-damaged elevation, whereas the placement of a leveling course atop damaged but un-milled pavement will tend to raise the surface of the roadway or some portion thereof above its original elevation. Roadway repair without milling can require the raising of road shoulders, guardrails and manhole covers and the adjustment of overpass clearances, all of which is unnecessary if a proper milling technique is employed. A use of milling prior to repaving can also permit ready establishment of the proper road grade and slope, and thereby avoid drainage and safety problems. Furthermore, milling typically provides a rough surface that readily accepts and bonds with the new asphalt or other pavement overlay. Finally, milling can provide raw material that can be reclaimed for use in the production of new paving materials.
A milling machine includes a milling drum with a plurality of cutter teeth mounted thereon which is contained within a milling drum housing. The milling machine is adapted to be advanced across a road surface to “mill” the surface to remove asphalt concrete pavement or Portland cement concrete pavement in preparation for recycling the pavement and/or in preparation for applying a pavement overlay. A milling machine typically includes one or more conveyors to take the milled material from the vicinity of the milling drum and direct it away from the machine and into an adjacent dump truck. A road stabilizer/reclaimer machine is similar to a milling machine in that it comprises a wheeled or track-driven vehicle that includes a milling drum with a plurality of cutter teeth mounted thereon which is contained within a milling drum housing. However, the milling drum of a road stabilizer/reclaimer machine is generally employed to mill or pulverized an existing road bed or roadway to a greater depth than does a milling machine prior to repaving (usually called reclaiming) or prior to initial paving (usually called stabilizing), and it leaves the pulverized material in place.
Cold In-place Recycling (“CIR”) equipment can be used to repair damage to a roadway in a single pass, while reusing essentially all of the existing asphalt material. In the CIR process, damaged layers of asphalt pavement are removed. The removed material is processed and replaced on the roadway and then compacted. If a roadway has good structural strength, CIR can be an effective treatment for all types of cracking, ruts and holes in asphalt pavement. CIR can be used to repair asphalt roadways damaged by fatigue (alligator) cracking, bleeding (of excess asphalt cement), block cracking, corrugation and shoving, joint reflective cracking, longitudinal cracking, patching, polished aggregate, potholes, raveling, rutting, slippage cracking, stripping and transverse (thermal) cracking. The root cause of the pavement failure should always be investigated to rule out base failure. However, CIR can almost always be used when there is no damage to the base of the roadway. Generally, CIR is only half as expensive as hot mix paving while providing approximately 80% of the strength of hot mix paving.
CIR can be carried out with the aid of a milling machine or a road stabilizer/reclaimer machine that has been modified by mounting an additive spray assembly in the milling drum housing to inject an asphalt additive such as an asphalt emulsion or foamed asphalt cement into the milling drum housing. The asphalt additive is then thoroughly blended with the milled material by the milling drum and can be left in a windrow or fed by the milling machine's discharge conveyor directly into a paving machine. Generally, the asphalt additive is supplied from a separate additive supply tanker truck that is coupled to the modified milling machine or the modified road stabilizer/reclaimer machine. The asphalt additive is drawn directly from the tank on the additive supply truck and pumped to the spray assembly in the milling drum housing.
Since the CIR process uses asphalt paving material that is already in place on the roadway, the only other component of the new pavement is the asphalt additive carried by the tanker truck. Consequently, conventional systems require that the modified milling machine or modified road stabilizer/reclaimer machine be coupled to the tanker truck during all phases of the CIR process. This makes it difficult to operate a CIR-modified machine around tight corners and through intersections. Consequently, it would be desirable if a method and apparatus could be provided that would allow an operator of a CIR-modified machine to continue to mill and process milled material through intersections, around tight corners and while switching out an empty tanker truck for a full one.